1. Field of the Invention
The invention relates generally to antenna feed systems, particularly in the microwave frequency bands.
2. Description of the Prior Art
A wealth of antenna coupling technology is extant in the prior art. The text "An Antenna Engineering Handbook." Henry Jasik. Editor, McGraw-Hill 1961 (first edition) describes much of this prior art. In addition, the text "Radar Handbook", Merrill Skolnick, Editor (McGraw Hill 1970) presents an overview of the state of this art at the time of its publication. That reference also serves to acquaint the reader with microwave system aspects requiring and utilizing circuits of the class to which the invention belongs.
In the prior art, stripline implementations of antenna multi-element feeds have frequently required rather complex trace cross-overs or connections between more than one plane of conductive traces. Single plane cross-overs inherently produce undesired coupling and the cost of manufacture of multi-plane devices is relatively high. The manner in which the invention contributes to this art to provide a simpler, more easily manufactured stripline feed network will be evident as this description proceeds.
Microwave stripline type components for related purposes are described in the patent literature, for example U.S. Pat. No. 4,460,877 entitled "Broad-band Printed Circuit Balun Employing Coupled-Strip All Pass Filters" and copending U.S. Pat. No. 4,578,652 issued Mar. 25, 1986 entitled Broadband Four-Port TEM Mode 180.degree. Printed Circuit Microwave Hybrid. Those disclosures show stripline implemented circuits in which the circuit traces are printed circuits held between parallel ground planes, as is the case for the invention. U.S. Pat. No. 3,518,688, discloses a low loss, high strength honeycomb arrangement for effecting the overall structure mechanically. That technique is applicable to the devices of the aforementioned patents and also to this invention.
The basis for the type of circuit coupling to form more than one beam, as employed in the invention, is examined in a paper included in the Transaction of IEEE, Vol. Ap-16, July 1968 pp. 436-440. The resulting feed concept has been referred to as a Lopez Feed.